[Feature Request] Auto-tile on other monitors when the active monitor has no tiles available

**Describe the bug**
Auto Tiling ignores other monitor(s)

**To Reproduce**
Steps to reproduce the behavior:
1. Enable Auto Tiling
2. Open windows until all tiles are used
3. Open one more window

**Information (please complete the following):**
- Tiling Shell version: 16.2
- GNOME version: 47.0

**Additional context**
On step 3, Tiling Shell should see that there are available tiles on a different monitor and use those. I'm not sure what to do in the case of 3+ monitors, though, perhaps allow the user to rank them in the extension settings.

Working on this might help with #277, particularly if the user is given authority to decide the auto-tiling order.